This protocol is designed to evaluate regional brain glucose metabolism in response to the administration of 0.4 mg/kg, 0.8 mg/kg of d-fenfluramine and placebo to test the hypothesis that fenfluramine-induced changes in brain metabolism of the orbital frontal cortex and adjacent ventral medial frontal cortex (primary hypothesis) as well as temporal and cingulate cortex (secondary hypotheses) are blunted in patients with impulsive/aggressive personality disorders.